In general, a fluorocarbon resin has excellent chemical resistance and has no water-absorption. Further, of various synthetic resins, the fluorocarbon resin has very excellent weatherability, thermal stability, abrasion resistance and non-tackiness.
Polytetrafluoroethylene (PTFE) is the representative polymer of fluorocarbon resin. PTFE is used as a corrosion resistant material for inner lining or packings in pipes of chemical apparatuses from the standpoints of a high thermal stability and an excellent chemical resistance; an insulating material for electric cables from the standpoints of a low dielectric constant and dielectric loss and a high resistivity; and a bearing or sliding material of non-oil supply from the standpoint of an excellent surface lubricating property.
However, since PTFE has a high melting point and is difficult to fuse, the moldability is poor and the molding must be conducted by sinter molding. Therefore, the moldability of PTFE has been improved by using a copolymer comprising tetrafluoroethylene and a fluorine-containing vinyl monomer other than the tetrafluoroethylene or olefin monomer, or a fluorine-containing resin which does not use tetrafluoroethylene, thereby obtaining a thermoplastic material having the characteristics of PTFE.
On the other hand, fluorocarbon resin has the above-described excellent characteristics but is expensive, and it is therefore considered that a laminate of the fluorocarbon resin and another inexpensive substrate is useful from a practical standpoint.
However, fluorocarbon resin is non-tacky and it is difficult to adhere it to another substrate.
Various methods have heretofore been proposed to improve the adhesion between fluorocarbon resin and another substrate. For example, a method comprising wet treating a surface of a fluorocarbon resin molding with an alkali metal solution and a method comprising a dry treating a surface of a fluorocarbon resin molding by means of a corrona discharge, plasma discharge, sputter etching, etc. are known as methods of improving the surface of the fluorocarbon resin so as to bond the fluorocarbon resin to another substrate with an adhesive. Other than these methods, a method comprising dissolving the surface of the fluorocarbon resin with a specific solvent to bond it to another substrate and a method comprising physically bonding the fluorocarbon resin to another substrate with a glass mat are known.
Further, adhesive resins which bond the fluorocarbon resin and another substrate have been proposed. For example, a specific ethylene-ethyl acrylate copolymer or ethylene-vinyl acetate copolymer or their modified products (Japanese Patent Published Unexamined Application Nos. 86748/81 and 12645/82), an epoxy group-containing polyolefin (Japanese Patent Published Unexamined Application Nos. 8155/82 and 212055/82), a resin composition of a methyl methacrylate copolymer onto which vinylidene fluoride is grafted and a methyl methacrylate polymer (Japanese Patent Published Unexamined Application No. 12646/82) and the like are known as such resins.
However, the above-described prior art is not satisfactory with respect to mold-processability or adhesion and there are restriction on the types of adherent. For example, a laminate of a thermoplastic fluorocarbon resin and an ethylene-vinyl acetate copolymer as disclosed in Japanese Patent Published Unexamined Application Nos. 86748/81 and 12645/82 has the disadvantage that when a large amount of vinyl acetate is introduced in the form of a copolymer with ethylene to improve the adhesion, the mechanical strength of the copolymer deteriorates and the adhesion strength is not improved.